"For many users with add-ons installed, this will significantly reduce Firefox's memory consumption, without requiring upgrades to those add-ons," he adds. "For those users, Firefox 15 is likely to be faster (sometimes drastically so) and less likely to crash, especially if they have multiple add-ons installed and/or keep Firefox running for a long time between restarts."

Nethercote explains that add-on memory leaks are caused by "zombie compartments," where information from web pages is stored and remains after you close a page or depart from it.

Firefox 15 cleans out those compartments, a move that its developers weren't entirely sure would work.

Much criticism has been leveled at Firefox since its inception over its piggish memory practices, but in recent months it has made great strides in its memory management. Last November, for instance, it put SpiderMonkey, the Javascript engine used by the browser, on a diet. And in May, it announced its campaign to plug memory leaks in add-ons.

In addition to better memory management, Firefox 15 also supports the Opus audio format. The format, which can be played directly in Firefox 15, offers better compression formats like MP3, Ogg, or AAC; is good for both music and speech; can dynamically adjust bitrate, audio bandwidth and coding delay; and supports both interactive and prerecorded applications.

"We think Opus is an incredible new format for web audio," Timothy Terriberry writes in a Mozilla blog. "We're working hard to convince other browsers to adopt it, to break the logjam over a common [audio] format."

The "prime time" version of Firefox 15 is scheduled for avaiability August 28.